Toward an Understanding of the Enhanced CO2 Electroreduction in NaCl Electrolyte over CoPc Molecule‐Implanted Graphitic Carbon Nitride Catalyst

Direct CO2 electrolysis in seawater enables the simultaneous conversion of CO2 into CO and the chlorine ions into Cl2, further meeting downstream industry needs such as phosgene synthesis and also facilitating the net consumption of CO2. As a result, the direct implementation of CO2 electrolysis in seawater is urgently required. Herein, a CoPc molecule‐implanted graphitic carbon nitride nanosheets (CoPc/g‐C3N4) electrocatalyst is prepared via a simple mechanochemistry method. The CoPc/g‐C3N4 with a negatively charged surface and preferential adsorption capability for Na+ can achieve appreciable faradaic efficiency (FE, 89.5%) toward CO with a current density of 16.0 mA cm−2 in natural seawater and also realize long‐term operation for 25 h in simulated seawater. Process monitoring further reveals that the chlorine ions in NaCl electrolyte can modulate the reaction microenvironment around the anode, which in turn has positive effects on the CO2RR in cathode. The CO2RR overall splitting in the simulated seawater exhibits a maximum FE of 98.1% towards CO at cell voltage of 3 V. This work describes the development of a carbon‐coupled CoPc molecular catalyst that can drive the CO2 electrolysis in simulated seawater and provides a promising and energy‐saving coupled reaction system for direct coproduction of CO and Cl2. A CoPc/g‐C3N4 catalyst with a negatively charged surface and preferential adsorption for Na+ is developed. It can be operated in simulated seawater, achieving high selectivity for CO and appreciable stability as well as demonstrating the concept of direct coproduction for CO and Cl2. The promoted CO2RR via the changed reaction microenvironment derived from the chlorine evolution reaction is revealed and decoupled.